1. Field of the Invention
The invention generally relates to a device for gripping and holding a component, and in particular, to a tool in the handling system of a machine tool.
2. Background Discussion
In program controlled machine tools and machining centers, different types of handling systems are used. On the one hand, some handling systems provide for the organized supply of certain workpieces to the work area of the machine and, on the other hand, systems may provide for the automated exchange of tools from a tool storage in the machining unit of the machine.
In the known tool storages for complex processing machines there are, among others, chain magazines, disk magazines, and shelf magazines in different embodiments. What all tool magazines have in common is a plurality of tool accommodations into which the tool cones of various processing tools are inserted in predetermined positions. Individual tools are taken from the magazines and inserted into and extracted from the processing unit by a motor-driven tool changing device in accordance with a predetermined processing program of the machine.
From German patent 101 63 294, a handling system for program-controlled milling and drilling machines is known which comprises a chain tool magazine disposed adjacent to the machine tool and a tool changing device carrying a gripper movable in a plurality of axes and comprising grapples which are angularly displaced with respect to each other. One grapple is intended to accommodate a used tool from the work spindle and a second grapple is intended to insert a new tool into the work spindle, respectively. On each chain link the vertical chain magazine comprises a tool accommodation, the accommodation aperture of which is defined by two radially protruding, rigid retainer fingers. At least one of the retainer fingers is attached to the associated chain link via a joint so that it is displaced against the force of a built-in spring during the insertion and extraction of a tool cone.
German patent 196 51 277 is directed to a disk magazine disposed next to the stand of a milling and drilling machine, the circular magazine disk of which is provided with clamp-like tool accommodations in regular intervals at its outer circumference. Above each tool accommodation an upper spring shackle is provided which exerts a downward acting force acting on the ring-shaped collar of an upwardly protruding tool cone and pushes the ring-shaped collar against the respective clamp-like tool accommodation. Each spring shackle comprises one soft elastic and one rigid retainer finger. The pressing force of the spring shackles, however, is insufficient to prevent the tools accommodated in the tool accommodations from falling out, even in case of high starting accelerations or braking decelerations. This known handling system comprises a tool changing device carrying a so-called double gripper on the free end of a swivel arm. The two grippers are displaced in right angles with respect to each other and comprise two gripping or retainer fingers, respectively, which define a central accommodation orifice. Both retainer fingers of each gripper are linked to a main body so as to be displaceable about a tappet and can be locked in their closed position against the spring force by a respective locking member. Due to the number of components, the tool accommodations of the magazine disk and the grippers of the tool changing device, respectively, require considerable technical expenditures.
German patent publication 42 15 697 A describes a tool changing device comprising two parallel grippers disposed on an arm which respectively form a tool accommodation. The grippers are linked to the arm so as to be rotatable about a transverse axis and comprise two rigid jaws surrounding a recess, one of the jaws being rigid and the other pivotable against the spring force in a joint. The resulting spreading of both jaws allows the insertion of a standardized tool holder into the tool accommodation. Due to the number of individual components the grippers are technically complex and susceptible to failure. A similar tool gripper comprising two gripping jaws pivotable with respect to each other is known from the German publication OS 37 17 201. An operating element causing the two gripper jaws to be spread or closed is moved by a thrust block fixedly mounted on the machine. This gripper is also particularly complex in design.
European application EP 0 355 271 A describes a tool gripper for a tool handling system of a machine tool comprising a plate-like support member provided with two elastically spreadable jaws or retainer fingers defining a common accommodation orifice for the tool cone to be clamped. The support plate comprising the integrally formed retainer fingers is integrally formed of a technical plastic, for example, of an acetal resin. To prevent the clamped tools from unintentionally disengaging, for example, when starting or braking a chain magazine, the disengagement force for extracting a tool from an accommodation orifice should be considerably larger than the insertion force. For this purpose a plurality of integrated resilient bridges are respectively formed as laminated springs between parallel slots in the bottom section of the accommodation orifice in the support plate made of synthetic resin. The laminated springs and the slots extend transverse to the jaws or the longitudinal axis of the gripper and have a low spring constant in the transverse direction as well as a relatively high spring constant in the longitudinal direction. Due to the material properties of the support plate used and the design and arrangement of the integrated laminated springs, this gripper is unsuitable for handling heavy tools.